[x264-devel] Re: problem with X264 over Itanium - IA64

[Guillaume POIRIER]

Hi,

On 4/20/06, Henri-Pierre Charles <hpcharles at gmail.com> wrote:

> We are testing X264 (versions 20-03-006 & 21-03-2006) to apply various
> optimizations.

What kind of optimizations do you have in mind?


> While executing it over IA64 architecture, it produces
> unaligned memory access errors.
>
> Most probably in encoder/analyse.c due to following lines
>
>  *(uint64_t*)mvc[0] = *(uint64_t*)a->l0.me16x16.mv;
>  *(uint64_t*)mvc[i_mvc] = *(uint64_t*)m->mv;)
>
>  Is there any patch/solution available for that?

I suppose GCC has some pragmas to force aligment by using padding...


> Is it related to the
> fact that the ia64 is a 64bits architecture ?

Among the platforms supported by x264 is the PPC64, which, like most
RISC cpu (like Sparc), has strong aligment restrictions, so I'm
surprised that you experience unaligned access problems and PPC64
users don't (but maybe it's because no userland app runs in 64bits
mode on PPC64, like on early Sparc64).
x86-64 is a special case as all aligment is allowed.

> Are you aware if somebody has worked on the ia64 yet ?

Nope... but if I recall correctly, XviD (www.xvid.org) has some
Itanium1 optimization code, if ever that can be significant for you.

Guillaume
--
I am disillusioned enough to know that no man's opinion on any subject
is worth a damn unless backed up with enough genuine information to
make him really know what he's talking about.

-- H. P. Lovecraft (about the flamewars on FFmpeg and MPlayer-dev mailing lists)
http://www.brainyquote.com/quotes/quotes/h/hplovecr278144.html

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